1. Field of the Invention
The present invention relates generally to firearms having reciprocating cartridge handling elements such as slides or bolts and which are automatically operated by recoil force, or gas pressure, or a combination thereof, upon firing, for feeding cartridges from a magazine to the cartridge chamber of a firearm barrel and for extracting and ejecting the cases of spent cartridges. More specifically, the present invention has effective application in semi-automatic or fully automatic firearms of the type having a recoil force operated, or gas pressure operated, or a combination thereof, spring returned reciprocating bolt, or a slide with integral bolt, which extracts and ejects the cartridge cases of spent cartridges from the cartridge chamber of the gun barrel during its rearward or recoil movement of the bolt or slide, and which feeds cartridges from a cartridge magazine into the cartridge chamber of the gun barrel during the bolt or slide forward or returned movement.
2. Description of the Related Art
The firearms industry offers many caliber and cartridge configurations for use. Of particular popularity with recreational, sport, and match shooters are the small caliber, high velocity rounds currently available. One example is the .22 Magnum cartridge. The terms .22 Magnum, .22 WMR and .22 Winchester® Magnum Rimfire are used interchangeably herein to refer to a widely known ammunition which is commercially available from many sources. Another example of a small caliber, high velocity round is the .17 HMR.
The firearms industry has been trying to produce a semi-automatic .22 Magnum for many years with very little success. In spite of the poor performance by many of the .22 magnum semi-automatics available, the firearm is still highly sought after because of the spectacular performance of the round itself. The high velocity round has a flat trajectory with little recoil. Many firearms manufacturers would like to produce a .22 Magnum weapon but, simply do not pursue one due to some inherit problems associated with cartridges of this type. A common problem associated with the .22 Magnum semi-automatics available is a failure to cycle the firearm mechanism upon firing, and to extract the spent cartridge reliably.
In a typical center-fire cartridge as used in a firearm. The cartridge has a cylindrical case body, with one end closed, and is typically made of a brass alloy. The closed end of the cartridge case has a primer cap inserted within and opening in the center of the closed end. A bullet is inserted into the opposing end of the brass case. The body of the cartridge case is filled with gunpowder, or as referred to herein “propellant.” Upon the firing pin of the firearm striking the primer cap, the primer cap, ignites, or burns. The ignited primer cap then ignites the propellant within the cartridge case. The pressure created by the ignited propellant then drives the bullet out of the cartridge case and down the rifled barrel of the firearm. As will be appreciated by those skilled in the art, rim-fire cartridge designs are also used in many firearms. The propellant in a rim-fire cartridge is ignited by striking the rim of the cartridge case by the firing pin of the firearm.
In a firearm mechanism, the brass cartridge is driven back into the bolt face due to the propellant pressure. In blowback enabled firearm mechanism, as are known in the art, the force of the cartridge case upon the bolt face is utilized to cycle the mechanism. Other types of firearm mechanism, such as recoil, gas operated, blow-forward, and assisted blowback, all fully, or partially, utilize the force of the brass cartridge upon the bolt face to cycle the firearm mechanism.
It is known in the art that certain dissimilar metals tend to stick to each other if very high pressure is applied. The temporary mechanical bond of dissimilar metals under high pressure was discovered by a naval armament engineer named John Blish. This principle of metal-to-metal adhesion in firearms is known as the “Blish principle” or “Blish effect.” This adhesive force is due to static friction between the two dissimilar metallic surfaces of the cartridge case and barrel chamber being driven together at high pressures. The Blish effect is used to advantage in the firing chambers of most cartridge firearms. When a cartridge ignites within a firearm chamber, the brass cartridge case expands against the steel chamber of the barrel causing a temporary static bond, and high friction, between the walls of the barrel chamber and the cartridge case. This bond is desirable when it comes to firearms because it allows the cartridge case to swell, or obturate, thus sealing the chamber preventing gases from escaping. A secondary effect reduces the foot pounds of thrust on the breech face exerted by the cartridge case due to the exploding gun powder, or propellant, within.
In the case of the .22 Magnum, and other cartridge rounds known in the art, the Blish effect may preclude proper cycling of the firearm mechanism. The brass of the cartridge, is driven into contact with the steel of the barrel chamber by the pressure of the exploding powder. The brass cartridge expands within the chamber due to the propellant pressure, and the static bond of the Blish effect locks the cartridge within the chamber. The static bond remains until the propellant pressure has reduced, and the cartridge is then forced back against the bolt. The Blish effect thereby reduces the force applied to the bolt face of the firearm mechanism. As the cartridge case begins to withdraw from the chamber, the dynamic friction between the expanded cartridge case and chamber, further reduce the force applied to the bolt face of the firearm mechanism. The firearm mechanism may fail to cycle properly because of the diminished force applied to the bolt face by the cartridge. Specifically, the .22 Magnum cartridge will often fail to cycle the firearm mechanism, and fail to eject, because it is temporarily adhered to the chamber walls within firearm barrel even as the bullet exits the barrel. In order for any .22 Magnum semi-automatic to function properly and reliably cycle, this problem must be remedied.
In the case of the 22 Magnum in a semi-automatic pistol this static bond lasts longer than it takes for the high velocity bullet to exit the barrel leaving little energy remaining to cycle the firearm mechanism. The shorter the barrel, as in the case of pistols, the less energy there is available to operate the firearm mechanism. After the bullet exits the barrel, the pressure within the firearm chamber and bore quickly dissipates. Compounding the problem, the .22 Magnum contains a relatively light powder charge, supplying little energy to cycle the firearm mechanism.
A discussion of propellant pressures generated in the chamber and barrel of a firearm is disclosed in U.S. Pat. No. 1,131,319, issued to Blish. Within the Blish patent, the principal of dissimilar metal adhesion under pressure is used to advantage. The Blish patent discloses essentially a breech locking mechanism that could be used on a blowback operated firearm. The breech locking mechanism delays the blowback of the bolt until the chamber pressure has diminished to an acceptable level.
With the popularity of the new small caliber, high velocity, flat trajectory rounds in the shooting community, a demand to use the rounds in existing firearms has been created. Many recreation and sport shooters own multiple handguns or rifles chambered in more traditional calibers such as .45 ACP and 9 mm Parabellum. It would be desirable to provide a means of replacing the barrels and bolts of existing firearms with components configured to fire the new small caliber, high velocity cartridges. The re-use of the frame, receiver, trigger group, safety group, and other stock components of existing firearms with new components configured for use with the new cartridges would represent a significant cost savings to the shooting enthusiast. Moreover, the firearm may be readily converted back to the prior, more traditional, caliber when desired by reinstallation of the old stock components.
According, it would be advantageous to provide a barrel assembly to allow the use of the new small caliber, high velocity rounds reliably in an automatic or semi-automatic firearm. Such a barrel assembly would provide an accurate platform for use of the cartridge, while aiding the reliable and consistent cycling of the firearm mechanism. The barrel assembly would also be configured for ease of manufacture in high volumes, and be of a robust construction to ensure the safety and integrity of the barrel assembly over the life of the firearm. It would also be advantageous to provide a firearm conversion kit to enable the conversion of the barrel and bolt assembly of existing firearms to fire the new small caliber, high velocity rounds. It is thus to such a firearm barrel assembly that the present invention is primarily directed.